Chem Lab-1

• Sample heated too much in air
• Darkening or effervescence of the sample

Different crystalline forms of the same compound which have different but sharp melting points.

Compounds that cystallize with water incorporated in their crystal latice in a definite proportion by weight.

Hydrates melt at a different temp than the anhydrous compound.

A pair of enantiomers. The enantiomers have identical melting points, but together as a racemic mixture they do not melt at that temperature and show characteristics of an impure compound.

The minimum melting point of a mixture.

• -non-ideal mixtures
• -distill at a constant boiling point
• -constant composition
• -behave as a single pure compound

pressure must remain constant.

• - Does not react with the compound to be purified
• -Dissolves a moderately large amount of compound when "boiling" hot
• -Dissolves a small amount of compound when at room temp.
• -Is able to remove impurities. Impurities should either be highly soluble or highly insoluble.

• -Distribution coefficient)
• -Partition coefficient K_D

dissolving NaCl in the water layer to increase the distribution coefficient of an organic compound in the organic solvent.